Nixie Tube Clock

So as you can see in the video above, I made a nixie tube clock. It looks something like this (infact it looks exactly like this, because this is a picture of it):

The clock up and running

Below is the schematic for the project, as you can see I'm using 6 IN12 nixie tubes, each with it's own 74141 nixie tube driver. These drivers are great! They simply connect directly to the nixies and display whatever 4 bit binary number you give them (if you give them anything above 9 they blank the display - hence why I use the number 10 in my code to blank the nixies). Because they take in a simple 4 bit binary number, I can hook them directly up to some shift registers to drive them, in my case I used 3 74HC595 shift registers (available everywhere), because they can be "daisy chained" together, meaning in the code I only have to write one 24 bit binary number and it will display all 6 numbers on the nixies. Though in reality I split them up into pairs and write three 8 bit binary numbers.

To use the 74141s you need to connect the live pin of the nixies (through a resistor - in my case 1k5) to the high voltage supply, and then each pin to it's corresponding pin on the driver, which can be found on the datasheet. On my board I forgot these 1k5 resistors and had to modify it. My original board had the live pins going straight to the supply, so I had to cut that trace on the board, and botch in some resistors to each of the tubes, the result is below:

For my main chip I'm using an ATMega328P (the same chip as is in the Arduino Uno), and I'm running the arduino bootloader on it so I can program it in the arduino language - just to make things simpler.

It is interfacing with a DS3232 real time clock chip, which I would highly recommend! It is a great chip which holds hours, minutes, seconds, year, month, date, day of the week (all of which are adjusted for leap years automatically) and it has a tonne of usable SRAM inside it. It's also really really accurate, with a temperature compensated crystal oscillator inside the chip, and fairly easy to interface with (though early on I had some issues - I think it was too much capacitance on the line as I was testing it with cables plugged into the chip socket) over I2C. The only downside I can see is it only comes in a SMD package, which I know some people don't like soldering. Unfortunately I don't have a picture of it, as it's tucked underneath the coin cell battery holder.

For the high voltage supply I simply ordered one of eBay, as it was simpler and cheaper than designing my own! The one I used was this one.

HV Supply board

For the case to my project I laser cut an acrylic front and back and used some chunky nuts and bolts I had lying around to hold them together, as well as to hold the PCB in.

As mentioned in the video, there is a bug free board available on OSHPark if you want to order my board and build this yourselves, and all my code is up on github, links in the banner to where you can find all that!

Homebrew GPS

Hey Guys,

So this project isn’t actually new, I did this around a year and a half ago, but it’s still cool (I think) and still relevant so I may as well share it. This is my homebrew GPS unit!

So the first thing you may notice is it’s not exactly neat, well hey? I did it with very few resources, and for what I made it with, I think it’s quite good!

GPS Top View


The main micro-controller I’m using is an ATMega328, in the form of an Arduino Pro Mini (available from sparkfun). Now I know I’ve talked about this before but I really love this board, it’s small, perfect for embedding in projects, and cheap! What more could you want? The GPS I’m using is the Adafruit Ultimate GPS, which I believe is THE best hobbiest GPS. The OLED screen is also from Adafruit, and again is great value for money! It’s tiny (perfect for this project) but still has really high contrast and therefore readability. Both the GPS and screen have wonderful libraries written for them too, which makes the coding so much easier! Aside from the GPS, the screen and the Micro, the only other things are the batteries (AAA) and the buttons, which I soldered onto stripboard with 10K pull-downs (though later I realised it would’ve been easier to use the ATMega328’s internal pull-ups).

Most of the effort with this project was the code, which by the way is awful. I did this code when I was 14, and well it shows. So don’t be too scared! You can find the code on my GitHub page (link up top), so go take a look!

If you can’t stand the sight of such awful code (and I wouldn’t blame you), you can browse the pictures below, which are much more sightly!



Sparkfun Dumpster Dive!

Hey guys!

So recently I ordered a Sparkfun Dumpster Dive from, well, Sparkfun… Above is the video of me unboxing it. If you want to see the photos in a bit higher detail, then check below, also links to most of the products can be found below too (the ones I could find).

I unbox a Sparkfun Dumpster Dive box!

Dumpster Dive Link:

Eval Board for MAX2000-RAX:

Connecters: You try finding them 😛


Arduino Cellular Shield:

GPS Eval Board: Can’t find any info on this… I assume it was a production test run or something…

Incremental Rotary Encoder:

Motor with Gearbox: Again, can’t find it…

Ultra Sonic Range Finder:

Pieces of plywood: Go to your local hardware store

More Connectors: See last set of connectors

Ethernet connector:

Opto-Interrupter: Not worth posting a link, you can get them everywhere…

Battery Holders:

Tactile Switch:

TWR-K60N512 Freescale Tower Module:


Tremolo Effects Pedal – Part 2!

So you may recall I was designing a tremolo effects pedal for my friend. Well I got the boards back (lovely quality from OSHPark) and soldered them up and, well see for yourself!

Tremolo - Entire Circuit

Above is the circuit for the project, which I have broken down into little bits. Hopefully it’ll be easier to understand that way!

Tremolo Power

So I’ll start with the simplest bit! The power section. It’s pretty much what it looks like, power comes in from headers, and is switched, with a switch.

Tremolo Voltage Divider

The next simplest bit is probably this bit, which is just a voltage divider to give us a nice 4.5V, and some smoothing capacitors across the supply rails. We need the 4.5V because this is what the signal will be centred on, and putting it directly in the middle of the supply rails makes it easier on the op-amp. Op-amps generally don’t work as well closer to the supply rails, and most of the time don’t output near them, to do this, you need a special kind of op-amp, referred to as a rail-to-rail op-amp.

Tremolo Sine Wave Gen

The next bit is the sine wave generator, this is a phase-shift oscillator configuration, with the op-amp for stability (without this op-amp if we were to try to draw any current out of the PSO the sine wave would collapse). RV1 and RV2 are potentiometers controlling the amount of modulation, and the frequency of modulation respectively.

Tremolo Modulator

The final section is the modulator itself! This is the bit where the sine wave is used to modulate the signal from the instrument. The modulation is actually applied to the feedback loop of the op-amp with the transistor (BC548) the op-amp then applies this to the signal itself. The capacitor on the output is to block the DC component of the signal (the 4.5V) and leave the signal as just the amplitude modulated input.

So that’s it! I will eventually be selling this as a kit, but until then, you can order the rev.1 board from OSHPark!

Cheers, Tom

Tremolo Effects Pedal

So for my friends birthday, I decided I’d get him something a little more personal than just a bar of chocolate say, or some money. So I set out to design and build him a Tremolo effects pedal for guitar!

First of course, I needed to figure out how a Tremolo pedal works, I’d heard one in action before, but never thought about what was going on in any depth. Tremolo is an effect created when you change the amplitude of the waveform, which basically changes the volume of the sound. The speed at which you modulate (change) the volume can be changed on the pedal, as can the amount it varies it.

With this in mind, I got to work on EagleCAD (a free schematic and PCB layout software package) designing my pedal. Of course I didn’t design it all from scratch, I patched different circuits together to create it:


This circuit essentially works like this: The bottom section, with the four capacitors, is a sine wave generator. Hooked up to an op-amp (LM324), so as to make sure current could be drawn from it (without the op-amp, if you attempted to use the sine wave signal for anything, it would collapse). There are two potentiometers here, R1 is the potentiometer controlling the amount of modulation the sine wave applies to the signal, R2 is controlling the frequency. The modulation is physically applied to the feedback loop of the top op-amp (another LM324) through the transistor, which then applies it to the signal.

The power, ground, input, output and switch terminals are so they can be connected to their appropriate off board components.

After designing this schematic, I created a PCB:

Tremolo Board


I am currently waiting for my PCB to be built (by OSHPark), but when I get them back and test them, I will write another post. If they work, I may even sell them as a kit!

Leave any feedback (pun intended) below.

Cheers, Tom


Want to see what a SeedBoard can do? Check this post!

Note: SeedBoards are currently not for sale, but if you really want one drop me an e-mail and I will get in contact!

So big(ish) news guys! Me and my co-partner Jacob Rawson have been developing a small micro-controller dev board in our spare time, because we got sick of having to spend loads of money on an Arduino simply to embed it in a project and never see it again.

Now, there are other solutions to this rather than building your own, though much less fun, like the Sparkfun Pro Mini (which I have mentioned before)! For most of you this will be perfectly adequate but for me, living in the UK, it was just a tad too expensive to ship over here.

So why not build one? I got myself onto EagleCAD and started designing a board! This is the result! The SeedBoard (currently rev.2). With a small square form factor it’s ideal for embedding in a project, and (obviously) cheap enough! Costing us around £6 (~$10) non-profit. It can have any crystal you want in it, up to the chip limit of 20MHz, although if you’re feeling adventurous, you could try over-clocking it?

Thanks go to OSHPark for the amazing quality boards they consistently produce, this being one of them!

They are currently not for sale, but (as mentioned above) if you really want one, drop me an e-mail ( and I’m sure we can work something out!

For those who don’t want one just yet though, we may be running a kickstarter sometime next year!

Look out for that!


CastAR – Kickstarter!

Hey everyone!

So for the few of you who have been living in a dumpster recently, Jeri Ellsworth and Rick Johnson, have been developing one of (what I think is) the coolest advances in gaming of the 21st century! A new kind of Augmented Reality glasses, castAR!








If you want a much better explanation of what it is and how it works and what it is there are many places I can send you, chief of which kinda has to be their website. Aside from that, Jeri has a pretty amazing youtube channel, and did a great interview about it on the amp hour (another must if you are into electronics).

But if you insist on listening to me and not them, I shall give you as detailed explanation as I can with the limited knowledge of the technology I have.

Basically, in a normal augmented reality system (such as google glass), the light is projected from a pico projector directly into your eye through some kind of prism. And this is all well and good, except because they have no reference to the real world, so to get around focussing issues, they focus the picture at infinity! Now this creates a great picture, but it doesn’t half confuse your eyes, because they put it into context with the rest of the picture, and with context it being focussed at infinity doesn’t make any sense! This can cause some issues such as headaches and nausea when using such glasses.

So what’s so special about castAR that made me call it “one of the coolest advances in gaming of the 21st century”? Well it’s quite a simple change, that changes alot. Instead of projecting the light directly into your eyes, these glasses project it out, towards a special kind of surface called a retrorelective surface. This is a special kind of surface which reflects pretty much all light directly back at you, meaning you can project a picture out to this surface and see it brilliantly clearly without your eyes getting confused over where to focus, because it all makes sense to your eyes with the world around it! This surface can also be used with multiple glasses at once.

Not only does this eliminate nausea and headaches, but the team at castAR have put in IR leds to the retroreflective surface, giving the glasses a reference point with which to render images onto. Allowing complete 3D rendering that is not only locked to the surface, but also allows you to walk around the render and it give realistic views of the object from all angles. From what I understand this is achieved by having each of the IR leds to pulse at different frequencies which can be identified by the glasses and used as reference points.

Add to this the wand they have created with more IR leds, which allows the user to interact with this 3D world (In one example the wand was used to knock over a jenga tower) and you get an inclusive, non-painful, interactive, gaming system for as many people as you like.

CastAR Wand







So what’s not to like?

Go check out the kickstarter campaign running at the moment for the glasses! 

Thanks all! And thanks to Jeri and Rick for developing such a cool gaming system!

Blutooth Audio Link – Video!

Above is a video about my Bluetooth Audio Link board REV.1.

My revision 2 board is currently up on OSHPark, so go check that out!

Also if you have got a rev.1 board here are the instructions for making it work properly! Unfortunately there were some design changes needing to be made which I overlooked on rev.1. So here are the instructions:

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In response to Corey, who requested a parts list for BAL Rev.2. Below is the Parts List for the REV.2 board, as exported from eagle, hope this helps:

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Here is the schematic for the board:
BAL Schematic

VFD Tube Clock

Hey people!

So a while ago I bought an old Vacuum Florescent Display tube, and attempted to build my own controller for it. Well I’ll keep that story brief but it doesn’t need saying that I failed dramatically, and blew about £60 on it ($96).

But I didn’t give up and a couple of weeks ago I bought myself an awesome little board from OSHPark. Built by a user named ‘Awesomenesser’. Unfortunately I have no means of contacting this person but I would sincerely like to thank him/her for making this awesome little board.

Built by Awesomenesser

Built by Awesomenesser

The board itself uses a MAX6921AUI. Which is a VFD controller chip made by maxim integrated. This chip is absolutely awesome so if you are thinking of doing a VFD project really do check it out!

Unfortunately the board was supplied with no instructions so I sat down for a while and compared data-sheets until I had something that made sense. Now I don’t want you to have to do the same thing so I thought I’d do a little picture and you can see for yourself how it goes.

Max6921AWI Breakout Explained

Some of you who know a thing about VFD tubes will know they run at high voltages, between 30 and 80 gives you a good bright light (though make sure not to exceed the 76V rating on the chip). So you may be wondering how I generated this. To do this I used the HCJ-IPM-V5 DC-DC step up converter, I would highly recommend this solution for anyone wanting up to 30V DC, simply because it is SO easy and simple and still very cheap.

DC-DC Step Up Converter


I also used a DS1307+ chip, to keep the time, with a 32.768KhZ watch crystal and a simple 3V coin cell to keep it running when off. I used a really useful library called RTCDue to interface this chip with my Arduino Due, though I plan on eventually running it on an ATMega328PU, in which case I will use this DS1307+ library from Adafruit.



And finally I used the Arduino Due to run the show. My code is available on gitHub so take a look if you are looking to interface with the MAX6921 chip! The library I use is specifically for the arduino Due, but if you change that the code should work perfectly on any other arduino!


Bluetooth Audio Link

UPDATE: The BAL project has now been redesigned, check the BAL section on the header to see the changes!

Hey everyone,

So after successfully completing my RGB LED strip lights, I was at a loss for what project to embark on next. I wanted to make something a bit more flashy, and a bit more well built.

That is when I saw this video from Sparkfun, where they used an RN-52 Bluetooth module to stream audio directly from a phone into speakers. Now this on it's own is no real use to me, but streaming it to an audio jack where I could plug in headphones or plug it into my full speaker system at home? That's useful (and cool)!!!

The video:

So I went onto EagleCAD, and started designing, finally creating this lovely little board:

Bluetooth Music Link


The design is chiefly pretty much the same as the sparkfun circuit, but instead of streaming it out to speakers, it has an audio jack. It also has a DC power jack with an onboard 3.3V supply. The switch is used to switch it between programming mode and normal mode.

If you are interested in the schematic, that is here:

Bluetooth Audio Link Schematic

As of yet, whilst I am still prototyping it, most of the components are through-hole, but if you want to order the board to try it out, it is available from OSHPark (which is where I ordered mine from).

WARNING, on the silkscreen, the LED's are backwards, if you order it make sure you put them the other way!

If you wish to make a board professionally, I seriously recommend OSHPark! They have amazing quality, and amazing prices too, and if you are not fussed about waiting, free international shipping. They are also run by a pretty cool guy called Laen, who is great.

Cheers all,

Tom Cousins